Method and apparatus for making lamp filament joints



Dec. 19, 1950 A. H. WEBER 2,534,540

mamon AND APPARATUS FOR MAKING LAMP FILAMENT JOINTS Filed July 31, 1946 2 Sheets-Sheet 1 FIG. L

mm VIII/577176 M five TORI ORNEY.

Dec. 19, 1950 A. H. WEBER msmon AND APPARATUS FOR MAKING LAMP FILAMENT JOINTS 2 Sheets-Sheet 2 Filed July 31, 1946 FIG. 6.

FIG. 5.

FIG. 9.

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A RNEY.

Patented Dec. 19, 1950 METHOD AND APPARATUS FOR MAKING LAMP FILAMENT JOINTS Alfred H. Weber, Kirkwood, Mm, anignor to North American Electric Lamp Company, St. Louis, Mo., a corporation of Missouri Application July 31, 1946, Serial No. 887,274

4 Claims. 1

My invention pertains to a method and apparatus for producing a good conductive connection between the fllament and the lead-in wires of a carbon fllament incandescent electric lamp.

The present usual method of forming such connection by hand application or carbon paste to the joined ends of the wires and filament is tedious and results'in a substantial percentage of imperfect joints and in frequent breakage of filaments. My object is to avoid manual application of material to the wire-filament joints and to provide means for much more rapid and uniform formation of efllcient and durable conductive connection between these parts. I also achieve improvement in rigidity and permanence oi their physical connection under shocks incident to shipment and handling of the lamps.

In achieving the objects stated I. employ thermal deposition of carbon from a hydrocarbon fluid, such as benzine or naphtha as examples, and provide means for raising to incandescence, and while immersed in the fluid, only those parts of the carbon filament adjacent the physical connection between iilament and lead-in wires. The molecules of the hydrocarbon fluid adjacent the heated filament ends and the heated tips of the associated lead-in wires are broken down and a-progressive deposition of carbon on these parts occurs during continued maintenance or the high temperature.

In the accompanying drawings, which illustrate apparatus embodying my invention, Figure l is a top plan view of mechanism for positioning and handling lead-in wires and associated filament in carrying out my method of forming a desired Joint, this view showing a duplicate set oi said means; Figure 2 is a side view of one of the handling means shown in Figure 1; Figure 3 is a vertical sectional view on the line 8-4 of Figure 2 showing the filament short-circuiting bar and its support; Figure 4 is a sectional view along the line 4-4 01' Figure 2; Figure 5 illustrates the lead-in wires molded in the glass base portion or the lamp and having their illament receiving ends flattened, and Figure 6 shows these flattened ends bent around the ends of the filament to form a physical support for the filament during the subsequent Joint forming operation; Figure 7 is a cross-section on the line l--7 of Figure 6; Figure 8 illustrates a completed Joint, and Figure 9 shows a completed carbon filament lamp; Figure 10 is a diagram illustrating an electric circuit which may be employed to apply variable current to the portions of the filament to be heated.

The numeral l indicates an open top rectangular container (or hydrocarbon fluid, such as bensine, this container being located in a larger box 2 whereby a body of inert gas, such as CO2, may be constantly maintained above the hydrocarbon fluid under the condition that the fluid employed is inflammable. Pivotally mounted at 22 in the bottom of the container i is a vertical supporting plate 3 in the upper end oi which is pivotally mounted a short-cir" cuiting bar 4 preferably 0! silver, said bar being supported at its center for free tilting in either direction from the horizontal plane. One tilted position is indicated by dotted lines in Figure 3 and the relation of fluid level to the position of the bar is indicated by the dash line in Figure 2.

The means illustrated for supporting and rotating the lead-in wires and filament assembly into and out of the hydrocarbon fluid comprises a frame 6 of insulating material, to the upper surface of which on each side is secured electrically conductive strips of metal 8 having down-turned ear portions 1 pivotally supported at B on standards ii secured to the bottom of the fluid container i.

As indicated in Figure 5 for example, during the process of manufacture of a lamp the tube I0 through which air is to be exhausted from the bulb is secured to the glass supporting base ii for the lead-in wires and forms means (or physically securing the glass base and associated parts to the pivoted insulating frame 5, said glass tube being insertable through the circular opening in the forward part of the insulating irame (see Figure 4). The bell-shaped bottom of the glass insulator is positioned adjacent the forward end 0! the frame. The outer ends of v the lead-in wires are clamped in contact with the metal strips 6 by means of clamping membars [2 attached to an insulating plate l3, which plate is supported at one end from the frame element ii by means of a screw it, this being a sufllciently loose connection that the forward end of plate I! may be moved against action of the clamping spring l5 thereby spacing the upper part or the wire clamping portion l2 from the upper portions oi the strips ii for ready insertion and removal of lead-in wires.

The position oi the center of gravity of the assembly consisting of the supporting frame and the lead-in wires and associated parts is adjustable by means of movable weight 2i and is so located that the assembly will rotate, under the influence of its own weight, into the position in which the filament is brought into contact with the short-circuiting bar 4. The assembly is removable from joint forming position by lever l6 engageable with the under surface of the plate 13. Lever I6 is operable by handle its, both of the elements being non-rotatively secured to the rotatable shaft indicated in Figure 2. Motion of the operating handle I80. toward full line position withdraws support from the pivoted frame and the assembly moves by its own weight to convey the filament into operating position in contact with the short-circuiting bar beneath the surface of the fluid. The filament is, of course, very frangible and in order that motion of the parts to operating position against the short-circuiting bar may not be sufficiently rapid to break the filament, the center of sravity of the assembly comprising frame and parts carled thereby is located close to the vertical plane through pivots 8.

As previously stated, the plate 3 carryin the short-circuiting bar 4 is pivoted at 22 and a triangular positioning clement ll of insulating material is also pivoted at 22 through its metal supporting frame Ila. An adjusting screw 23 passes through an opening in plate 3 and is threaded into Ila, a spring l8 between I! and plate 3 maintaining the adjusted spacing between the plate and the element ll. When the filament is moved toward joint forming position in the bath, the forward edge of the positioning element i'l contacts with the forward edge of the insulating lamp base at a point between the lead-in wires before the filament contacts the short-circuiting bar; engaging surface of I! continued motion of the lamp base rotates l1 and the support 3 until the filament engages the short-circuiting bar 4. The fixed relation between parts 11 and 3 determines that contact of the bar 4 with the filament will be at approximately constant distance from the ends of the lead-in wires notwithstanding slight variations in longitudinal positions of the lamp bases with reference to frame 5 when mounting them thereon. The adjusting screw 23 affords means for varying the relative position of the short-clrcuiting bar and the forward edge of the positioning element I! to enable the apparatus to handle lamp bases having shorter or longer lead-in wires.

In order to assure contact with the shortcircuiting bar with ends of the filament whereby the remainder of the filament will actually be eliminated from the operating electric circuit, the bar is freely rotatable on its pivot. Thus variations in relation of the plane of the filament ends to the horizontal will not prevent the necessary short-circuiting of the remainder of the filament.

In Figure l the filament supporting and shortclrcuiting apparatus is shown in duplicate, the operatin circuits thereof being connected in series whereby the contact joints for two lamps can be simultaneously formed. A suitable current supply means for the electrical circuit indicated in Figure 1, is diagrammatically shown in Figure in which the voltage in the secondary of the transformer 18 which applies the heating current during the joint forming operation can be varied by means of an adjustable transformer 20 connected to an electric power source.

The operation of the apparatus will be apparent from the foregoing description. When the parts are in the position shown in Figure 2 Due to the inclined and current is applied, the short portions of the filament between the short-circuiting bar and the lead-in wires will be raised to a relatively high temperature. Also, part of the filament within the crimped ends of the lead-in wires may be highly heated, depending upon the slicetive points of electrical contact between the lead-in wires and the filament which may be established by crimping the wire ends around the filament. In any event the tips of the lead-in wires, being in contact with hot filament ends, will also be highly heated. The current is so adjusted that the temperature of the current carrying portions of the filament and the tips of the lead-in wires is high enough to cause break-down of the hydrocarbon composition coming into contact therewith and resultin in deposition of carbon. The deposited carbon is also highly heated thereby causing progressive depositing of carbon and the application of current is continued long enough to produce deposit of sufficient carbon to form a satisfactory electrical connection between the filament and the lead-in wires for lamp operation and to form a relatively rigid connection between the filament and the lead-in wires. Completed joints are indicated at 24 in Figure 8. At the beginning of the joint forming operation only sufllcient current is applied to bring the ends of the filament to the temperature which will cause break-down of the hydrocarbon fiuid (this condition being ascertained by release of gas from the bath), it being desirable to avoid a temperature high enough to render the filament sufilciently pliable to bend under the gravity force effective on the assemblage. After some carbon is deposited and the rigidity of the heated portions of the filament thus somewhat increased, the current is gradually increased partly as the result of gradual reduction of resistance in the circuit due to the deposit of carbon and partly by application of increased voltage, the current being brought to approximately 20 amperes as a maximum by the time the carbon joint has reached the desired size.

It will be understood that I do not limit myself to the use of any specific carbon bearing bath since the desired result can be obtained with the use of any enveloping gas or liquid from which carbon will be progressively deposited to form a firm mass as the result of the high temperature of the joint parts during application of current.

Having fully described my invention, that which I claim as novel and desire to protect by Letters Patent of the United states is:

1. An apparatus for making lamp filament joints comprising an open-top rectangular container for a hydrocarbon material decomposable by heat, a vertical supporting plate pivotally mounted on the bottom of said container, at short-circuiting bar tiltably mounted at the upper end of said plate, a positioning element pivotally mounted adjacent the support plate, an adjusting screw suitably connecting the positioning element and support plate whereby the spatial relationship between same may be determined, a frame member pivotally mounted in the bottom of said container in longitudinal axial alignment with the support plate and positioning e .ient, said frame having spaced electroconductive strips, an insulated plate member attached to said strips and provided with clamps, and lever means for lifting said frame.

2. An apparatus for making lamp filament mined, a frame member pivotally mounted in the bottom of said container in longitudinal axial alignment with the support plate and positioning element, said frame having spaced electroconductive strips, an insulated plate member attached to said frame, and means for adjusting the center of gravity of the frame for controlling the speed with which the frame pivots down-- wardly from lifted position.

3. An apparatus for making lamp filament joints comprising an open-top rectangular container for a hydrocarbon material decomposable by heat, a vertical supporting plate pivotally mounted in the bottom of said container, a shortcircuiting bar tiltably mounted at the upper end of said plate, a triangular positioning element pivotally mounted adjacent the support plate and in axial alignment therewith, an adjusting screw suitably connecting the positioning element and support plate whereby the spatial relationship between same may be determined, a frame member pivotally mounted in the bottom of said container in longitudinal axial alignment with the support plate and positioning element, said frame having spaced electroconductive strips, an insulated plate member attached to said strips and provided with clamps, a lever for lifting said frame, and a movable Weight provided on said frame for adjusting the center of gravity of the frame for controlling the speed with which the frame pivots downwardly from lifted position.

4. In an apparatus for forming an electrically conductive joint between the lead-in wires and the ends of the filament for an incandescent L-li) 6 electric lamp comprising an open-top rectangular container for a hydrocarbon material decomposable by heat, a frame member pivotally mounted in the bottom of said container, electroconductive strips provided on said frame, an insulated plate member attached to said strips and provided with clamps whereby the lead-in wires may be releasably supported in contact with the strips, the ends of the lead-in wires being attached to the ends of the lamp filament, a vertical supporting plate pivotally mounted in the bottom of said container in spaced axial aligned relationship with the frame member, a short-circuiting bar tiltably disposed on the upper end of said support plate, a triangular positioning element pivotally mounted on the bottom of the container adjacent the support plate and between said support plate and frame, an adjusting screw suitably connecting the positioning element and support plate whereby the spatial relationship therebetween may be determined, a lever for lifting said frame, a movable weight provided on said frame for adjusting the center of gravity of the frame to control the rate of descent of the frame in pivoting downwardly from lifted position in bringing the end portions of the filament into contact with the short-circuiting bar, and means for supplying electrical current to the circuit which comprises the strips, the lead-in wires, the ends of the filament, and the short circuit bar.

ALFRED H. WEBER.

REFERENCES CITED The foilowing references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 383,484 Packard May 29, 1888 391,815 Packard Oct. 30, 1888 392,159 Lemp Oct. 30, 1888 1,600,974 Brueckmann Sept. 28, 1926 

